Alena Kalendova

Kinetics and mechanism of the biodegradation of PLA/clay nanocomposites during thermophilic phase of composting process

The degradation mechanism and kinetics of polylactic acid (PLA) nanocomposite films, containing various commercially available native or organo-modified montmorillonites (MMT) prepared by melt blending, were studied under composting conditions in thermophilic phase of process and during abiotic hydrolysis and compared to the pure polymer. Described first order kinetic models were applied on the data from individual experiments by using non-linear regression procedures to calculate parameters characterizing aerobic composting and abiotic hydrolysis, such as carbon mineralization, hydrolysis rate constants and the length of lag phase. The study showed that the addition of nanoclay enhanced the biodegradation of PLA nanocomposites under composting conditions, when compared with pure PLA, particularly by shortening the lag phase at the beginning of the process. Whereas the lag phase of pure PLA was observed within 27days, the onset of CO2 evolution for PLA with native MMT was detected after just 20days, and from 13 to 16days for PLA with organo-modified MMT. Similarly, the hydrolysis rate constants determined tended to be higher for PLA with organo-modified MMT, particularly for the sample PLA-10A with fastest degradation, in comparison with pure PLA. The acceleration of chain scission in PLA with nanoclays was confirmed by determining the resultant rate constants for the hydrolytical chain scission. The critical molecular weight for the hydrolysis of PLA was observed to be higher than the critical molecular weight for onset of PLA mineralization, suggesting that PLA chains must be further shortened so as to be assimilated by microorganisms. In conclusion, MMT fillers do not represent an obstacle to acceptance of the investigated materials in composting facilities.

Utilization of Waste Lignin and Hydrolysate From Chromium Tanned Waste in Blends of Hot-Melt Extruded PVA-Starch

The demand for biodegradable plastic material is increasing worldwide. However, the cost remains high in comparison with common forms of plastic. Requirements comprise low cost, good UV-stability and mechanical properties, as well as solubility and water uptake lead to the preparation of multi-component polymer blends based on polyvinyl alcohol and starch in combination with waste products that are hard to utilize—waste lignin and hydrolysate extracted from chromium tanned waste. Surprisingly the addition of such waste products into PVA gives rise to blends with better biodegradability than commercial PVA in an aquatic aerobic environment with non-adapted activated sludge. These blends also exhibited greater solubility in the water and UV stability than commercial PVA. Tests on the processing properties of the blends (melt flow index, tensile strength and elongation at break of the films) as well as their mechanical properties showed that materials based on these blends might be applied in agriculture (for example as the systems for controlled-release pesticide or fertilizer) and, somewhat, in the packaging sector.

PLA based bionanocomposites and their transport properties

This paper deals with the evaluation of gas transport properties of bionanocomposites based on polylactic acid 2003D (PLA). Montmorillonite based fillers, Cloisite® 10A, 20A, 30B and natural Cloisite® Na+, were incorporated into PLA polymer films. PLA/clay mixtures were produced by twin screw extruder ZSK-25. Further testing sheets were prepared from PLA/clay mixtures by Brabender Plasti-Corder equipped by flat die. The prepared composites were evaluated for water absorption, permeability of gases and water vapors. Further material morphology was assessed using X-ray diffraction as well as transmission electron microscopy. The best results achieved compositions with PLA/Cloisite10A and Cloisite 30B.This paper deals with the evaluation of gas transport properties of bionanocomposites based on polylactic acid 2003D (PLA). Montmorillonite based fillers, Cloisite® 10A, 20A, 30B and natural Cloisite® Na+, were incorporated into PLA polymer films. PLA/clay mixtures were produced by twin screw extruder ZSK-25. Further testing sheets were prepared from PLA/clay mixtures by Brabender Plasti-Corder equipped by flat die. The prepared composites were evaluated for water absorption, permeability of gases and water vapors. Further material morphology was assessed using X-ray diffraction as well as transmission electron microscopy. The best results achieved compositions with PLA/Cloisite10A and Cloisite 30B.

EVA copolymer/clay nanocomposite films processing conditions and the effect on barrier properties

Nanocomposite materials with layered clay used as nanofiller and copolymer ethylene and vinyl acetate matrix (EVA, the content of VA component l9 wt. % and 5% wt.) were prepared by compounding the individual components in KO Buss kneader. The MMT Na+ and four types of commercial products such as Nanofil N 5 and N3000, Cloisite 93A and 30B were used as nanofillers. The quantity of all the above-mentioned nanofillers was 3 and 5 wt. % in relation to the content of montmorillonite. The aim was to evaluate the influence of VA content on resulting nanocomposite properties.The morphology of nanocomposite EVA/clay samples was examined by means of transmission electronic microscopy TEM. Furthermore, mechanical and especially barrier properties were observed.Despite the fact that the XRD and microscopy results have revealed that complete exfoliation did not take place in any case, mechanic properties as well as the permeability measurements show that 3% concentration of clay was enough to achieve the improvement o...

Permeation properties of polymer/clay nanocomposites

The important characteristics of polymer/clay nanocomposites are stability, barrier properties and in the case of polyvinyl chloride also plasticizer migration into other materials. Therefore, the permeation properties of polymer/clay nanocomposites are discussed in this paper. The attention was focused to the polyethylene (PE) and polyvinyl chloride (PVC). Natural type of montmorillonite MMTNa+ and modified types of montmorillonite from Southern Clay Products were used as the inorganic phase. As the compounding machine, one screw Buss KO-kneader was employed. The principal aim is to fully exfoliate the clay into polymer matrix and enhanced the permeation properties. Prepared samples were tested for O2 and CO2 permeability. Polymer/clay nanocomposite structure was determined on the base of X-ray diffraction and electron microscopy (TEM).

EFFECT OF THE CLAY MODIFICATION ON THE THERMAL PROPERTIES OF PVC

The intercalation of organic compound is necessary to functionalize the montmorillonite surface. So, the intercalation of diethylene glycol and polyethylene glycol and the influence of plasticizer, namely tricresyl phosphate and isodecyldiphenyl phosphate as co‐intercalating agents were studied. For the PVC/clay nanocomposites the suspension type of PVC was used and the compound was prepared by the melt intercalation method. Two kinds of MMT (Cloisite®Na+, Cloisite®30B) and laboratory modified MMT by intercalation (diethylene glycol, polyethylene glycol) and co‐intercalation (tricresyl phosphate and isodecildifenyl phosphate) agents were used for the set of nanocomposite samples. The thermal stability of nanocomposite specimens was tested using of thermo gravimetric analysis, DMA and pH method.